The present invention relates to an apparatus for seaming can ends to cylindrical cans which have been filled with contents.
One known can end seaming machine is disclosed in U.S. Pat. No. 1,929,339. A can after it has been filled with contents is delivered by a belt conveyor, then turned by a timing table, and a can end is placed on the can while the can is being turned and guided by a feed turret. Thereafter, the can is turned by a clincher turret while at the same time the end hook of the can end and the flange of the can are clinched by a clincher mechanism, after which the can end is finally fixed to the can by a double seamer mechanism.
When the filled can is turned by the timing table, the direction of feed of the can is continuously varied, thereby applying centrifugal forces to the contents of the can. At the time the can end is placed over the can, the can is speeded up by the feed turret and hence the contents of the can are subjected to inertia. When the can is turned by the clincher turret while the can end is being clinched to the can, the direction of feed of the can is also varied, and centrifugal forces are imposed on the contents of the can. The higher the speed at which the can is fed, the more difficult it becomes to prevent the contents from jumping out of the can.
According to the current practice in the can making industry, can ends are seamed to cans at a rate of 1,400 to 1,500 cans per minute. When the can end seaming process is performed at such a high speed, it is entirely impossible to prevent the contents from being thrown out of the can under the inertia and centrifugal forces produced at the high feed speed and the varying direction of feed.
If the seaming rate is increased while allowing the contents out of the cans, then the rate of production of cans is increased, but a large quantity of thrown-out contents is wasted and the cost of manufacture of the cans is increased.
U.S. Pat. No. 3,730,118 discloses an apparatus for seaming a can end to a filled can while the can is being horizontally supported and linearly fed at a predetermined speed. According to the disclosed apparatus, the end hook of the can end and the flange of the can are pressed against a linear clincher, and the can end is seamed to the can by rolling the can end and the can along the clincher.
However, the apparatus does not have means for pressing the can end to the can when the can end is crimped onto the can. Therefore, the can end may not reliably be crimped onto the can at times. Another problem is associated with the present trend for the reduction of the thickness or gauge of can ends and cans from the standpoint of providing a saving of the can material. When the end hook of a can end of reduced thickness and the flange of a can of reduced thickness are pressed against the linear clincher to crimp the can end onto the can, the can end and the can tend to be deformed under pressure, and the can end may not be reliably seamed to the can .
The same problem occurs when a metal can end is to be seamed to a can made of a thin plastic sheet.